Westaway has been in the role for the maximum six-year term permitted under the club's constitution.
He will hand over to Summers after the club's best and fairest, the Trevor Barker medal count, on September 6.
"As a member of the club for well over 40 years, it is an honour to be elected as the incoming president of the St Kilda Football Club," Summers said.
"The smooth transition to the new leadership team is an indication that the board is confident that we have the right people and structures in place to not only advance current strategies but to take on the challenges that the club and the football industry in general face."
Summers has been a board member for five years and is head of the club's auditing committee.
He is the managing director and CEO of residential developer AVJennings.
He has been an employee of the company and its related corporations since 1984 and a director since August, 1998.
Before becoming managing director and CEO in February 2009, Summers was the company's chief financial officer and finance director.
Westaway, who oversaw three grand final appearances and the establishment of the Seaford training base, said Summers was a solid replacement.
"I was flattered to have been given custody of the club as president of the club for the past six years," Westaway said.
"Peter is a very capable person to continue with our strategy to get us to where we need to be."
Twitter: @AFL_JenPhelan
